Regional specialization within the intestinal immune system. Nat Rev Immunol. 2014;14:667-685. [PMID: 25234148 DOI: 10.1038/nri3738]

Microbial micronutrient sharing, gut redox balance and keystone taxa as a basis for a new perspective to solutions targeting health from the gut

In health, the gut microbiome functions as a stable ecosystem maintaining overall balance and ensuring its own survival against environmental stressors through complex microbial interaction. This balance and protection from stressors is maintained through interactions both within the bacterial ecosystem as well as with its host. As a consequence, the gut microbiome plays a critical role in various physiological processes including maintaining the structure and function of the gut barrier, educating the gut immune system, and modulating the gut motor, digestive/absorptive, as well as neuroendocrine system all of which are crucial for human health and disease pathogenesis. Pre- and probiotics, widely available and clinically established, offer various health benefits primarily by beneficially modulating the gut microbiome. However, their clinical outcomes can vary significantly due to differences in host physiology, diets, individual microbiome compositions, and other environmental factors. This perspective paper highlights emerging scientific insights into the importance of microbial micronutrient sharing, gut redox balance, keystone species, and the gut barrier in maintaining a diverse and functional microbial ecosystem, and their relevance to human health. We propose a novel approach that targets microbial ecosystems and keystone taxa performance by supplying microbial micronutrients in the form of colon-delivered vitamins, and precision prebiotics [e.g. human milk oligosaccharides (HMOs) or synthetic glycans] as components of precisely tailored ingredient combinations to optimize human health. Such a strategy may effectively support and stabilize microbial ecosystems, providing a more robust and consistent approach across various individuals and environmental conditions, thus, overcoming the limitations of current single biotic solutions.

Gut microbiota in hepatocellular carcinoma immunotherapy: immune microenvironment remodeling and gut microbiota modification

Hepatocellular carcinoma (HCC) remains a leading cause of cancer-related mortality, with limited treatment options at advanced stages. The gut microbiota, a diverse community of microorganisms residing in the gastrointestinal tract, plays a pivotal role in regulating immune responses through the gut-liver axis. Emerging evidence underscores its impact on HCC progression and the efficacy of immunotherapy. This review explores the intricate interactions between gut microbiota and the immune system in HCC, with a focus on key immune cells and pathways involved in tumor immunity. Additionally, it highlights strategies for modulating the gut microbiota - such as fecal microbiota transplantation, dietary interventions, and probiotics - as potential approaches to enhancing immunotherapy outcomes. A deeper understanding of these mechanisms could pave the way for novel therapeutic strategies aimed at improving patient prognosis.

Dietary AiiO-AIO6 mitigated Aeromonas hydrophila-induced intestinal inflammation in juvenile grass carp (Ctenopharyngodon idella) involving in NF-κB signaling and pyroptosis

AiiO-AIO6 is a quorum-sensing quenching enzyme that could decrease the virulence of pathogenic bacteria, and improve animal immunity. However, the precise regulatory mechanism of AiiO-AIO6 on intestinal immunity remains unknown. Thus, this study aimed to reduce this knowledge gap. After feeding with graded levels of AIO-AIO6 (0.0 (un-supplemented group), 2.5, 5.0, 7.5, 10.0, and 12.5 U/g) for 70 days, juvenile grass carp was selected from each group for a 6-day Aeromonas hydrophila challenge test. Meanwhile, some other fish selected from un-supplemented control group were injected with saline as un-challenged control. Results showed that A. hydrophila infection increased enteritis morbidity, and caused intestinal inflammation in grass carp compared with saline group, while AiiO-AIO6 supplementation decreased enteritis morbidity, mitigated inflammatory cell infiltration, pyroptosis, and apoptosis in the intestine after A. hydrophila infection. Furthermore, both 5.0 and 7.5 U/g AiiO-AIO6 decreased gene expressions of tumor necrosis factor-α and interleukin-1β, and elevated gene expressions of transforming growth factor-β1 and IL-10, potentially associating with decreased NF-κB p65 and increased PPARγ signaling in the intestine. Supplementing 5.0 or 7.5 U/g AiiO-AIO6 also mitigated intestinal pyroptosis, as indicated by reduced mRNA levels of NLRP3, PYCARD, caspase-1, GSDME a, and GSDME b, and decreased protein levels of N-GSDME and IL-1β. Additionally, AiiO-AIO6 alleviated intestinal apoptosis, demonstrated by reduced gene expressions of pro-apoptotic genes apoptotic protease activating factor-1, Bcl-2 associated X protein, Fas ligand, and caspase-3, as well as c-Jun N-terminal kinase and mitogen-activated protein kinase p38, and elevated gene expressions of anti-apoptotic factors, B-cell lymphoma-2, myeloid cell leukemia 1, and inhibitor of apoptosis protein. Altogether, optimal levels of AiiO-AIO6 attenuated intestinal inflammation probably relating to down-regulated NF-κB signaling, and reduced NLRP3 and GSDME-mediated pyroptosis, and finally reduced apoptosis in the intestine of grass carp.

CD3γ/δ+ T cells and MCSFR+ macrophages are activated to produce IL-26 after bacterial infection in grass carp

Interleukin-26 (IL-26) belongs to the IL-10 cytokine family and exerts diverse biological functions in regulating immune responses in vertebrates. Although IL-26 has been extensively studied in mammals, the functions of IL-26 remain largely unexplored in lower vertebrates. In this study, we determined the tissue and cell sources of IL-26 using a monoclonal antibody (mAb) generated against grass carp (Ctenopharyngodon idella, Ci) IL-26, and investigated the responses of IL-26 producing cells to bacterial infection. We showed that the CiIL-26 mAb specifically recognized the recombinant CiIL-26 proteins expressed in the Escherichia coli and HEK293 cells. Flow cytometry analysis revealed that the CiIL-26 mAb could detect the intracellular CiIL-26 expressed in the HEK293 cells and CIK cells stimulated with inactivated Aeromonas hydrophila (A. hydrophila). Using confocal microscopy, we analyzed IL-26+ cells in various tissues of grass carp following infection with A. hydrophila. It was shown that the IL-26+ cells were significantly increased in the gills, head kidney, posterior intestine and spleen. Remarkably, for the first time, we observed that most IL-26+ cells were CD3γ/δ+ T cells and MCSFR+ monocytes/macrophages, which could be induced by A. hydrophila. Our findings highlight the essential roles of CD3γ/δ+/IL-26+ T cells and MCSFR+/IL-26+ macrophages in the immune defense against bacterial infections in fish.

The Duodenal Microenvironment in Functional Dyspepsia

Functional dyspepsia (FD) is a chronic gastrointestinal disorder without a readily identifiable organic cause, resulting in bothersome upper abdominal symptoms. It is a highly prevalent disorder of which the pathophysiology remains mostly elusive, despite intensive research efforts. However, recent studies have found alterations in the microenvironment of the duodenum in patients with FD. In this review we summarize the duodenal microenvironment in homeostatic conditions and the alterations found in patients with FD, highlighting the similarities and discrepancies between different studies. The most consistent findings, being an impaired duodenal barrier and duodenal immune activation, are reviewed. We discuss the potential triggers for these observed alterations, including psychological comorbidities, luminal alterations and food related triggers. In summary, this review presents the evidence of molecular and cellular changes in patients with FD, with an impaired duodenal barrier and activated mucosal eosinophils and mast cells, challenging the notion that FD is purely functional, and offering different targets for potential future treatments.

Specific MSI2 deletion maintains intestinal barrier integrity by down-regulating ILC3s-derived IL-17 a in mice with colitis

BACKGROUND

Ulcerative colitis (UC) is an inflammatory bowel disease with an unknown cause. Previous studies have shown that Group 3 innate lymphoid cells (ILC3s) are crucial for maintaining intestinal mucosal immune homeostasis by producing key cytokines such as IL-22 and IL-17 A. While the RNA-binding protein Musashi-2 (MSI2) is recognized as essential for promoting intestinal epithelial regeneration post-injury, its impact on immune regulation remains unclear. Therefore, we aim to investigate the protective mechanisms associated with ILC3s-specific MSI2 deletion in a mouse model of ulcerative colitis.

METHODS

Dextran sulfate sodium (DSS) was used to induce a mouse colitis model. Colitis severity was evaluated through weight loss, diarrhea, fecal traits, colon length, and pathological scoring. Transcriptome sequencing was utilized to identify differentially expressed genes in colon tissues. Flow cytometry was employed to measure the quantity and functionality of ILC3s. Western blot was conducted to analyze protein expression, while real-time polymerase chain reaction and enzyme-linked immunosorbent assay were employed to quantify inflammatory factors. Additionally, immunofluorescence, AB-PAS staining, and immunohistochemistry were employed to evaluate the integrity of the intestinal barrier.

RESULTS

Following DSS treatment, colon damage was milder in Msi2∆Rorc mice than in Msi2fl/fl mice. Transcriptomic analysis revealed the down-regulation of cytokines and pro-inflammatory factors in the colon tissue of Msi2∆Rorc mice. Flow cytometry showed that specific deletion of MSI2 reduced the infiltration of ILC3s in the intestinal lamina propria of Msi2∆Rorc mice and decreased IL-17 A production. The reduction of IL-17 A-mediated immune responses lessened inflammatory damage to the intestinal barrier, thereby reducing colitis severity.

CONCLUSIONS

Specific deletion of MSI2 alleviates DSS-induced colitis in mice by reducing ILC3s infiltration and IL-17 A secretion in the lamina propria of the colon. This decrease in inflammatory mediators and cell infiltration dampens the inflammatory response in the intestinal mucosa, helping to maintain the integrity of the intestinal barrier in mice with colitis. These findings enhance our understanding of UC pathogenesis and offer novel avenues for clinical diagnosis and treatment.

Intestinal-region-specific functions of AHR in intrinsic enteric neurons during infections

Intrinsic enteric neurons (iENs) form a crucial neuronal network within the myenteric and submucosal plexus of the gastrointestinal tract, primarily responsible for regulating gut peristalsis. The mechanisms by which iENs sense and integrate dietary and microbial signals to regulate intestinal homeostasis and inflammation remain unclear. Here, we showed that environmental sensor aryl hydrocarbon receptor (AHR) was expressed in different iEN subsets in the ileum and colon and that AHR ligands differentially modulated iEN activity in these regions. Genetic perturbation of Ahr in neurons increased iEN activation in the ileum but, conversely, decreased it in the colon in response to different intestinal pathogens. Furthermore, neuronal AHR deficiency enhanced the clearance of bacterial pathogens, which was associated with increased proliferation and abundance of group 3 innate lymphoid cells in the ileum. Together, our findings demonstrate the region-specific functions of AHR in neurons in response to infections.

Chronic Exposure to Fluxapyroxad Exacerbated Susceptibility to Colitis in Mice via a Gut Microbiota-Indole Derivatives-Th17/Treg Cell Balance Axis

Fluxapyroxad is the most commonly used succinate dehydrogenase inhibitor fungicide. This work investigated its adverse effects on colitis susceptibility and explored the underlying mechanisms based on a mouse model. After 13 weeks of exposure at the acceptable daily intake (ADI) level, fluxapyroxad exacerbated the susceptibility to colitis, impaired the intestinal barrier, and elevated proinflammatory cytokines and chemokines of the colon in mice. It was found that this toxic effect was caused by the disruption of the gut microbiome. Specifically, the abundance of Lachnospiraceae and Muribaculaceae decreased, while Desulfovibrionaceae and Eggerthellaceae increased. Altered microbiota reduced fecal indole derivatives, including indole-3-lactic acid (ILA), indole-3-acetic acid (IAA), and indole-3-acrylic acid (IArA), inhibiting aryl hydrocarbon receptor (AHR) activation, disrupting immune homeostasis by overactivating Th17 cells and insufficient Treg cell differentiation, and causing mild colonic inflammation. Oral antibiotic-treated mice and fecal transfer experiments validated the pathway. Susceptibility to colitis induced by fluxapyroxad was not detected in the oral antibiotic-treated mice. Fecal transfer of the disordered gut microbiota caused by fluxapyroxad could aggravate the severity of colitis in recipient oral antibiotic-treated mice that did not receive fluxapyroxad exposure. In conclusion, chronic fluxapyroxad exposure at the ADI level exacerbated colitis via a gut microbiota-indole derivatives-Treg/Th17 cell balance axis, offering a new risk assessment perspective of fluxapyroxad.

Impact of afatinib on intestinal and salivary IgA: Immune response alterations linked to gastrointestinal side effects

BACKGROUND

Afatinib, an oral molecular-targeted anticancer agent, is effective but causes significant gastrointestinal side effects. These effects are associated with EGFR inhibition in intestinal cells and changes in the microbiota.

OBJECTIVE

To investigate the effects of afatinib on intestinal mucosal immunity in rats, focusing on IgA levels in the intestine and saliva, and to understand the innate and acquired immune responses to these side effects.

METHODS

Male Wistar rats received afatinib (5.2 mg/kg) daily for 24 h (Day 1) and for 2 weeks (Day 14). Gene expression in the intestine was analyzed using quantitative polymerase chain reaction. IgA levels in the intestine and saliva were measured using enzyme-linked immunosorbent assay.

RESULTS

Afatinib suppressed α-defensin 5 and pIgR in the jejunum and ileum, indicating reduced innate immunity. It increased IgA levels in the intestine and saliva, suggesting altered acquired immunity. Salivary IgA levels significantly correlated with intestinal IgA levels.

CONCLUSIONS

Afatinib affects gastrointestinal mucosal immunity, suppresses innate defense, and alters IgA production. Salivary IgA could serve as a marker for monitoring these effects, aiding cancer therapy management.

Inflammation-Induced Th17 Cells Synergize with the Inflammation-Trained Microbiota to Mediate Host Resiliency Against Intestinal Injury

BACKGROUND AND AIMS

Inflammation can generate pathogenic Th17 cells and cause an inflammatory dysbiosis. In the context of inflammatory bowel disease (IBD), these inflammatory Th17 cells and dysbiotic microbiota may perpetuate injury to intestinal epithelial cells. However, many models of IBD like T-cell transfer colitis and IL-10-/- mice rely on the absence of regulatory pathways, so it is difficult to tell if inflammation can also induce protective Th17 cells.

METHODS

We subjected C57BL6, RAG1-/-, or JH-/- mice to systemic or gastrointestinal (GI) Citrobacter rodentium (Cr). Mice were then subjected to 2.5% dextran sodium sulfate (DSS) to cause epithelial injury. Fecal microbiota transfer was performed by bedding transfer and co-housing. Flow cytometry, qPCR, and histology were used to assess mucosal and systemic immune responses, cytokines, and tissue inflammation. 16s sequencing was used to assess gut bacterial taxonomy.

RESULTS

Transient inflammation with GI but not systemic Cr was protective against subsequent intestinal injury. This was replicated with sequential DSS collectively indicating that transient inflammation provides tissue-specific protection. Inflammatory Th17 cells that have a tissue-resident memory (TRM) signature expanded in the intestine. Experiments with reconstituted RAG1-/-, JH-/- mice, and cell trafficking inhibitors showed that inflammation-induced Th17 cells were required for protection. Fecal microbiota transfer showed that the inflammation-trained microbiota was necessary for protection, likely by maintaining protective Th17 cells in situ.

CONCLUSION

Inflammation can generate protective Th17 cells that synergize with the inflammation-trained microbiota to provide host resiliency against subsequent injury, indicating that inflammation-induced Th17 TRM T cells are heterogenous and contain protective subsets.

Interplay between gut microbiota and exosome dynamics in sleep apnea

Sleep-disordered breathing (SDB) is characterized by recurrent reductions or interruptions in airflow during sleep, termed hypopneas and apneas, respectively. SDB impairs sleep quality and is linked to substantive health issues including cardiovascular and metabolic disorders, as well as cognitive decline. Recent evidence suggests a link between gut microbiota (GM) composition and sleep apnea. Indeed, GM, a community of microorganisms residing in the gut, has emerged as a potential player in various diseases, and several studies have identified associations between sleep apnea and GM diversity along with shifts in bacterial populations. Additionally, the concept of "leaky gut," a compromised intestinal barrier with potentially increased inflammation, has emerged as another key player in the potential bidirectional relationship between GM and sleep apnea. One of the potential effectors could be extracellular vesicles (EVs) underlying gut-brain communication pathways that are relevant to sleep regulation and function. Thus, therapeutic implications afforded by targeting the GM or exosomes for sleep apnea management have surfaced as promising areas of research. This review explores current understanding of the relationship between GM, exosomes and sleep apnea, highlighting key research dynamics and potential mechanisms. A comprehensive review of the literature was conducted, focusing on studies investigating GM composition, intestinal barrier function and gut-brain communication in relation to sleep apnea.

A VSV-based oral rabies vaccine was sentineled by Peyer's patches and induced a timely and durable immune response

The global eradication of canine-mediated human rabies remains an ongoing public health priority. While conventional oral rabies vaccines (ORVs) have demonstrated partial success in interrupting zoonotic transmission, current formulations necessitate improvements in both immunogenic profiles and mechanistic clarity. Herein, we present a recombinant vesicular stomatitis virus (VSV)-vectored vaccine candidate (rVSVΔG-ERA-G) engineered to express the glycoprotein of the rabies virus (RABV) ERA strain, substituting the native VSV glycoprotein. Preclinical evaluation across multiple mammalian species (Mus musculus, Canis lupus familiaris, Felis catus, Vulpes lagopus, and Nyctereutes procyonoides) revealed rapid seroconversion and sustained neutralizing antibody responses. Challenge experiments demonstrated 100% survival efficacy in pre-exposure prophylaxis models, with partial protection observed in post-exposure scenarios. Safety assessments confirmed significant attenuation of neurotropism and absence of horizontal transmission or environmental shedding. Furthermore, evidence showed that rVSVΔG-ERA-G is recognized by Peyer's patches (PPs), where a cascade activation of immune cells occurred. From another perspective, the absence of functional microfold cells in PPs hampered the initiation and progression of immune responses. This proof-of-concept study establishes rVSVΔG-ERA-G as an ORV candidate with enhanced biosafety and cross-species immunogenicity. The elucidation of M cell-dependent mucosal priming mechanisms provides a rational framework for optimizing the targeted delivery of ORVs.

Importance of rectal over colon status in ulcerative colitis remission: the role of microinflammation and mucosal barrier dysfunction in relapse

BACKGROUND

Ulcerative colitis (UC) is a refractory inflammatory disease that affects the rectum and colon, with pivotal involvement of the rectal environment in relapse initiation. This study was conducted in two phases to examine the differences in gene expression between the rectum and colon and to identify relapse factors.

METHODS

In ***Study 1, RNA sequencing was performed on biopsies from the colon and rectum of patients with active UC, those with remission UC, and controls. In Study 2, the mucosal impedance (MI) values reflecting mucosal barrier function and the mRNA expression of tight junction proteins and inflammatory cytokines were examined in 32 patients with remission UC and 22 controls. Relapse was monitored prospectively.

RESULTS

In Study 1, comprehensive genetic analysis using RNA sequencing revealed distinct gene profiles in the rectum and sigmoid colon of patients with remission UC. The rectum of these patients exhibited an enriched immune response and apical junction phenotype with persistent upregulation of CLDN2 gene expression. In Study 2, even in patients with remission UC, the MI values in the rectum, but not in the sigmoid colon, were significantly decreased, whereas they were negatively correlated with CLDN2, IL-1β, and IL-6 expressions.

CONCLUSION

The status of the rectum in patients with remission UC differs from that of the colon, with microinflammation and impaired mucosal barrier function, which are associated with the upregulation of CLDN2, playing a role in relapse.

Protective Effect of Dietary Fiber on Blood Pressure and Vascular Dysfunction Through Regulation of Sympathetic Tone and Immune Response in Genetic Hypertension

The mechanisms underlying the antihypertensive effect of dietary fibers remain poorly understood. This study investigates whether dietary fiber supplementation can prevent cardiovascular damage and high blood pressure in a genetic model of neurogenic hypertension. Six-week-old male spontaneously hypertensive rats (SHR) and their respective normotensive control, Wistar Kyoto rats (WKY), were divided into four groups: Untreated WKY, untreated SHR, SHR treated with resistant starch (SHR + RS), and SHR treated with inulin-type fructans (SHR + ITF) for 12 weeks. Additionally, a faecal microbiota transplantation (FMT) experiment was conducted, transferring faecal content from treated SHR donors to recipient SHRs. A diet rich in RS fiber reduced vascular oxidative stress, inflammation, and high blood pressure. These protective effects were associated with a reshaped gut microbiota, leading to increased short-chain fatty acid production, reduced endotoxemia, decreased sympathetic activity, and a restored balance between Th17 and Treg lymphocytes in mesenteric lymph nodes and aorta. Elevated plasma levels of acetate and butyrate in the SHR + RS group correlated with increased expression of aortic GPR41, GRP43 and PPARδ. Conversely, ITF treatment failed to prevent hypertension or endothelial dysfunction in SHR. FMT from the SHR + RS group to recipient SHR partially replicated these beneficial effects. This study highlights the antihypertensive benefits of dietary insoluble RS fiber, which are attributed to enhanced short-chain fatty acids production in the gut. This leads to improved gut permeability, reduced sympathetic tone, and diminished vascular T-cell accumulation. Therefore, dietary interventions with RS fiber may offer promising therapeutic strategies for preventing hypertension.

Gut microbiota participates in polystyrene microplastics-induced defective implantation through impairing uterine receptivity

Microplastics (MPs) are widespread in global ecosystems and could pose risks to human health. However, crucial information on the impact of MP exposure on female reproductive health remains insufficient. In this study, we constructed an MP-exposure mice model through oral administration of polystyrene microplastics (PS-MPs) and found that it resulted in impaired uterine receptivity and defective implantation. An accumulation of plastic particles was detected in MP mice intestines. Metagenomic sequencing of feces samples indicated a structural and functional alteration of gut microbiota. Alistipes played a prominent role in MP biodegradation, while among the biodegradable functional genes, ACSL made the greatest contribution. Both had a significant increase in MP group, suggesting a potential occurrence of ferroptosis. Ferroptosis, a form of programmed cell death, is closely associated with uterine receptivity impairment and defective implantation. We detected MDA contents and ferroptosis-related proteins, and the results indicated the activation of ferroptosis in the process. Our research is the first to elucidate that exposure to MPs impairs uterine receptivity and results in deficient implantation, while also providing initial evidence that gut microbiota plays a critical role in this process.

Antigen Uptake in the Gut: An Underappreciated Piece to the Puzzle?

The mammalian gut is a vast, diverse, and dynamic single-layer epithelial surface exposed to trillions of microbes, microbial products, and the diet. Underlying this epithelium lies the largest collection of immune cells in the body; these cells encounter luminal substances to generate antigen-specific immune responses characterized by tolerance at homeostasis and inflammation during enteric infections. How the outcomes of antigen-specific tolerance and inflammation are appropriately balanced is a central question in mucosal immunology. Furthermore, how substances large enough to generate antigen-specific responses cross the epithelium and encounter the immune system in homeostasis and during inflammation remains largely unexplored. Here we discuss the challenges presented to the gut immune system, the identified pathways by which luminal substances cross the epithelium, and insights suggesting that the pathways used by substances to cross the epithelium affect the ensuing immune response.

scRNA-seq of the intestine reveals the key role of mast cells in early gut dysfunction associated with acute pancreatitis

BACKGROUND

Intestinal barrier dysfunction is a prevalent and varied manifestation of acute pancreatitis (AP). Molecular mechanisms underlying the early intestinal barrier in AP remain poorly understood.

AIM

To explore the biological processes and mechanisms of intestinal injury associated with AP, and to find potential targets for early prevention or treatment of intestinal barrier injury.

METHODS

This study utilized single-cell RNA sequencing of the small intestine, alongside in vitro and in vivo experiments, to examine intestinal barrier function homeostasis during the early stages of AP and explore involved biological processes and potential mechanisms.

RESULTS

Seventeen major cell types and 33232 cells were identified across all samples, including normal, AP1 (4x caerulein injections, animals sacrificed 2 h after the last injection), and AP2 (8x caerulein injections, animals sacrificed 4 h after the last injection). An average of 980 genes per cell was found in the normal intestine, compared to 927 in the AP1 intestine and 1382 in the AP2 intestine. B cells, dendritic cells, mast cells (MCs), and monocytes in AP1 and AP2 showed reduced numbers compared to the normal intestine. Enterocytes, brush cells, enteroendocrine cells, and goblet cells maintained numbers similar to the normal intestine, while cytotoxic T cells and natural killer (NK) cells increased. Enterocytes in early AP exhibited elevated programmed cell death and intestinal barrier dysfunction but retained absorption capabilities. Cytotoxic T cells and NK cells showed enhanced pathogen-fighting abilities. Activated MCs, secreted chemokine (C-C motif) ligand 5 (CCL5), promoted neutrophil and macrophage infiltration and contributed to barrier dysfunction.

CONCLUSION

These findings enrich our understanding of biological processes and mechanisms in AP-associated intestinal injury, suggesting that CCL5 from MCs is a potential target for addressing dysfunction.

Gut microbiota in the development and progression of chronic liver diseases: Gut microbiota-liver axis

The gut microbiota (GM) is a highly dynamic ecology whose density and composition can be influenced by a wide range of internal and external factors. Thus, "How do GM, which can have commensal, pathological, and mutualistic relationships with us, affect human health?" has become the most popular research issue in recent years. Numerous studies have demonstrated that the trillions of microorganisms that inhabit the human body can alter host physiology in a variety of systems, such as metabolism, immunology, cardiovascular health, and neurons. The GM may have a role in the development of a number of clinical disorders by producing bioactive peptides, including neurotransmitters, short-chain fatty acids, branched-chain amino acids, intestinal hormones, and secondary bile acid conversion. These bioactive peptides enter the portal circulatory system through the gut-liver axis and play a role in the development of chronic liver diseases, cirrhosis, and hepatic encephalopathy. This procedure is still unclear and quite complex. In this study, we aim to discuss the contribution of GM to the development of liver diseases, its effects on the progression of existing chronic liver disease, and to address the basic mechanisms of the intestinal microbiota-liver axis in the light of recent publications that may inspire the future.

Bifidobacterium longum subsp. longum XZ01 delays the progression of colon cancer in mice through the interaction between the microbial spatial distribution and tumour immunity

Studies have shown that the colonisation of active microorganisms is more conducive to the development of tumour immunotherapy, but intuitive evidence regarding shaping of the tumour immune microenvironment is lacking. In this study, we used Bifidobacterium longum subsp. longum (XZ01) to intervene in a colon cancer mouse model and found that its mechanism may be related to the interaction between the spatial distribution of microorganisms and tumour immunity. Through the visualisation method we established, for the first time, we showed that harmful active bacteria such as Streptococcus and Rhodococcus specifically accumulate in the middle and upper layers of tumour tissue. These bacteria likely participate in signalling pathways that affect macrophages by directly contacting or invading the macrophages, leading to a nondifferentiated state in macrophages and the loss of some immune functions. Furthermore, the accumulation of Streptococcus and Rhodococcus fragments in the deep layer of tumour tissue likely upregulates the expression of IL-10 in tumour tissue and inhibits other immune cells, such as CD8+ T cells, DC and NK cells. In contrast, XZ01 can specifically compete for the growth sites of Streptococcus and Rhodococcus in the middle and upper layers of tumour tissue and probably protects macrophages from being invaded by harmful bacteria. XZ01 directly regulates the polarisation of M0 macrophages towards the M1 phenotype by upregulating IFN-γ, thus activating tumour immunity to inhibit the growth of tumour cells. This study revealed that the influence of active microorganisms on the tumour immune microenvironment is crucial for effective immunotherapy intervention, potentially offering new targets for improving patient prognosis.

Introducing a Novel Personalized Microbiome-Based Treatment for Inflammatory Bowel Disease: Results from NostraBiome's Internal Validation Study

Background/Objectives: Inflammatory bowel disease (IBD), encompassing ulcerative colitis and Crohn's disease, is characterized by chronic gut inflammation driven by microbial dysbiosis and immune dysfunction. Current therapies primarily involve anti-inflammatory and immunomodulatory strategies; however, many patients experience an inadequate response or a gradual loss of efficacy over time. This study evaluates the clinical efficacy of personalized microbiome modulation (PMM)-an AI-driven intervention designed to restore microbial balance and improve key treatment outcomes such as symptom control and remission rates. Methods: This was a single-arm, open-label validation trial involving 27 patients with moderate-to-severe IBD who had experienced prior treatment failure. Participants underwent three months of PMM, which included personalized dietary modifications, targeted probiotic supplementation, and antimicrobial interventions based on gut microbiome sequencing. Primary outcomes included stool frequency and consistency as well as inflammatory markers (C-reactive protein and fecal calprotectin), while secondary outcomes assessed nutritional status, metabolic function, and quality of life. Statistical analyses included paired t-tests and repeated measures ANOVA to determine significant changes over time. Results: PMM led to significant clinical improvements, including a 58% reduction in stool frequency (p < 0.001) and improved stool consistency. CRP and fecal calprotectin levels decreased markedly (p < 0.001), suggesting reduced systemic inflammation. Additionally, iron, vitamin B12, and vitamin D deficiencies improved (p < 0.001), alongside weight gain and increased energy levels. Notably, patients on anti-TNF biologics showed enhanced response rates, suggesting potential synergistic effects between microbiome modulation and biologic therapy. Conclusions: This study highlights PMM as a promising adjunctive therapy for IBD, demonstrating benefits across clinical, inflammatory, and metabolic parameters. While findings support the role of microbiome-targeted interventions in disease management, larger randomized controlled trials are required to confirm the long-term efficacy and applicability in broader patient populations.

Modulation of intestinal signal transduction pathways: Implications on gut health and disease

The gastrointestinal (GI) tract is essential for nutrient absorption and protection against pathogens and toxins. Its epithelial lining undergoes continuous renewal every 3-5 days, driven by intestinal stem cells (ISCs). ISCs are primarily of two types: actively proliferating crypt base columnar cells (CBCs), marked by Lgr5 expression, and quiescent label-retaining cells (+4 LRCs), which act as reserves during stress or injury. Key signaling pathways, such as Wnt/β-catenin, Notch, bone morphogenetic proteins (BMPs), and epidermal growth factor (EGF), are crucial in maintaining epithelial homeostasis. These pathways regulate ISCs proliferation and their differentiation into specialized epithelial cells, including goblet cells, paneth cells, enteroendocrine cells, and enterocytes. Disruptions in ISCs signaling can arise from extrinsic factors (e.g., dietary additives, heavy metals, pathogens) or intrinsic factors (e.g., genetic mutations, metabolic changes). Such disruptions impair tight junction integrity, induce inflammation, and promote gut dysbiosis, often perpetuating a cycle of intestinal dysfunction. Chronic ISCs dysregulation is linked to severe intestinal disorders, including colorectal cancer (CRC) and inflammatory bowel disease (IBD). This review emphasizes the critical role of ISCs in maintaining epithelial renewal and how various factors disrupt their signaling pathways, jeopardizing intestinal health and contributing to diseases. It also underscores the importance of protecting ISCs function to mitigate the risk of inflammation-related disorders. It highlights how understanding these regulatory mechanisms could guide therapeutic strategies for preserving GI tract integrity and treating related conditions.

Role of Mushroom Polysaccharides in Modulation of GI Homeostasis and Protection of GI Barrier

Edible and medicinal mushroom polysaccharides (EMMPs) have been widely studied for their various biological activities. It has been shown that EMMPs could modulate microbiota in the large intestine and improve intestinal health. However, the role of EMMPs in protecting the gastric barrier, regulating gastric microbiota, and improving gastric health cannot be ignored. Hence, this review will elucidate the effect of EMMPs on gastric and intestinal barriers, with emphasis on the interaction of EMMPs with microbiota in maintaining overall gastrointestinal health. Additionally, this review highlights the gastroprotective effects and underlying mechanisms of EMMPs against gastric mucosa injury, gastritis, gastric ulcer, and gastric cancer. Furthermore, the effects of EMMPs on intestinal diseases, including inflammatory bowel disease, colorectal cancer, and intestinal infection, are also summarized. This review will also discuss the future perspective and challenges in the use of EMMPs as a dietary supplement or a nutraceutical in preventing and treating gastrointestinal diseases.

Compartmentalized Human Immunodeficiency Virus Type 1 Reservoir in Intestinal Monocytes/Macrophages on Antiretroviral Therapy

BACKGROUND

The intestinal mucosa contains many cells targeted by human immunodeficiency virus type 1 (HIV-1), and high levels of HIV-1 DNA persist in this compartment under antiretroviral therapy (ART). While CD4+ T cells are the best-characterized reservoir of HIV-1, the role of long-lived intestinal macrophages in HIV-1 persistence on ART remains controversial.

METHODS

We collected duodenal and colonic biopsies from 12 people with HIV (PWH) on suppressive ART, enrolled in the ARNS EP61 GALT study. Total, integrated, intact and defective HIV-1 proviruses were quantified from sorted T cells and monocytes/macrophages. HIV-1 env quasispecies were analyzed by single-molecule next-generation sequencing and env-pseudotyped viruses were constructed to assess macrophage versus T-tropism.

RESULTS

Total HIV-1 DNA levels in intestinal T cells were significantly higher than those in monocytes/macrophages (P < .0001). Unintegrated HIV-1 DNA was detected in one-third of T-cell and monocyte/macrophage-positive samples. Intact HIV-1 proviruses were detected using the intact proviral DNA assay in 4 of 16 T-cell samples and 1 of 6 monocyte/macrophage samples with detectable HIV-1 DNA. HIV-1 sequences were compartmentalized between intestinal monocytes/macrophages and T cells in some subjects. Phenotypic analysis of pseudotyped viruses expressing HIV-1 envelopes from colonic monocytes/macrophages revealed T-tropism rather than M-tropism.

CONCLUSIONS

Our results show that monocytes/macrophages from the intestinal mucosa of PWH on ART can contain HIV-1 DNA, including intact or unintegrated forms, but at much lower levels than those found in T cells, and with some compartmentalization, although they do not exhibit a specific macrophage tropism, raising the question of the mechanisms of infection involved.

Production and Functional Evaluation of Recombinant Active Peptide RH in Pichia Pastoris: Protection Against Escherichia Coli Induced Cell Death

In the gastro-intestinal tract, Escherichia coli (E.coli) infections can trigger programmed cell death of intestinal epithelial cells, through mechanisms such as oxidative stress and ferroptosis, which compromise gut barrier integrity. Given the rising prevalence of antibiotic-resistant E. coli strains, there is an urgent need to develop innovative antimicrobial therapies that go beyond conventional antibiotics. Antimicrobial peptides represent a promising alternative for combating resistant bacterial strains due to their dual role in antimicrobial activity and immune modulation. In this study, we constructed multiple expression cassettes to express porcine β-defensin 2 (PBD2)-derived peptide RH in Pichia pastoris (P. pastoris), purified the peptide using nickel column affinity chromatography, and assessed its in vivo and in vitro activity. The results indicated that under the optimal condition (3% methanol), the total secreted protein concentration reached 306.5 mg/L after 120 h of fermentation. Following purification, the yield of recombinant active peptide RH (rRH) can reached 59.34 mg/L. The rRH exhibits strong antimicrobial activity and resistance to oxidation, and by inhibiting oxidative stress-mediated ferroptosis it reduces E. coli-induced cell death and injury in the jejunum. This dual functionality of rRH positions it as a potential therapeutic candidate for treating gastrointestinal infections and improving gut health, providing a crucial alternative to traditional antibiotics.

Advancements in the investigation of gut microbiota-based strategies for stroke prevention and treatment

Stroke represents a predominant cause of mortality and disability on a global scale, impacting millions annually and exerting a considerable strain on healthcare systems. The incidence of stroke exhibits regional variability, with ischemic stroke accounting for the majority of occurrences. Post-stroke complications, such as cognitive impairment, motor dysfunction, and recurrent stroke, profoundly affect patients' quality of life. Recent advancements have elucidated the microbiota-gut-brain axis (MGBA), underscoring the complex interplay between gut health and brain function. Dysbiosis, characterized by an imbalance in gut microbiota, is significantly linked to an elevated risk of stroke and unfavorable outcomes. The MGBA plays a crucial role in modulating immune function, neurotransmitter levels, and metabolic byproducts, which may intensify neuroinflammation and impair cerebral health. This review elucidates the role of MGBA in stroke pathophysiology and explores potential gut-targeted therapeutic strategies to reduce stroke risk and promote recovery, including probiotics, prebiotics, pharmacological interventions, and dietary modifications. However, the current prevention and treatment strategies based on intestinal flora still face many problems, such as the large difference of individual intestinal flora, the stability of efficacy, and the long-term safety need to be considered. Further research needs to be strengthened to promote its better application in clinical practice.

CXCR3 inhibition ameliorates mitochondrial function to mitigate oxidative damage through NCOA4-mediated ferritinophagy and improves the gut microbiota in mice

Nuclear receptor coactivator 4 (NCOA4)-mediated ferritinophagy contributes to maintain intracellular iron balance by regulating ferritin degradation, which is essential for redox homeostasis. CXC-motif chemokine receptor 3 (CXCR3) is involved in the regulation of oxidative stress and autophagy. However, its role in modulating intestinal oxidative damage through ferritinophagy and the gut microbiota remains unclear. In this study, the impacts of CXCR3 inhibition on intestine oxidative damage, ferritinophagy, and the gut microbiota, as well as the mitochondrial quality control were investigated both in vivo and in vitro. The results show that CXCR3 inhibition by AMG487 relieves Diquat-induced intestinal damage, enhances the expression of tight junction proteins, and promotes antioxidant capacity in mice. Simultaneously, CXCR3 inhibition improves gut microbiota composition, and triggers NCOA4-mediated ferritinophagy. Mechanistically, the effects of CXCR3 inhibition on ferritinophagy were explored in IPEC-J2 cells. Co-localization and interaction between CXCR3 and NCOA4 were observed. Downregulation of NCOA4-mediated ferritinophagy leads to increase the expression of tight junction proteins, reduces iron levels, restricts ROS accumulation, and enhances GPX4 expression. Moreover, CXCR3 suppression facilitates mitochondrial biogenesis and mitochondrial fusion, increases antioxidative capacity, and results in the elevation of tight junction proteins expression. These findings suggest that CXCR3 inhibition reverses Diquat-induced intestinal oxidative damage, enhances mitochondrial function, and improves gut microbiota composition by elevating NCOA4-mediated ferritinophagy, which implies that CXCR3 may serve as a potential therapeutic intervention targeting iron metabolism for treating intestinal diseases.

Zinc Deficiency Reduces Intestinal Secretory Immunoglobulin A and Induces Inflammatory Responses via the Gut-Liver Axis

Nutritional zinc (Zn) deficiency could impair immune function and affect bowel conditions. However, the mechanism by which Zn deficiency affects the immune function of gut-associated lymphoid tissue (GALT) remains unclear. We investigated how Zn deficiency affects the function of GALT and level of secretory IgA (sIgA), a key component of the intestinal immune barrier, its underlying mechanisms, and whether Zn deficiency induces bacterial translocation to the liver. As previous research has indicated that interleukin (IL)-4 administration or Zn supplementation has a beneficial effect on the spleen of Zn-deficient rats, we investigated whether these supplements reverse the GALT immune system. Five-week-old male rats were fed a standard diet, Zn-deficient diet supplemented with saline or IL-4 for 6 weeks, or Zn-deficient diet followed by a standard diet for 4 weeks. Zn deficiency suppressed sIgA secretion in the intestinal tract by affecting GALT function and induced inflammatory responses through bacterial translocation to the liver via the portal vein. Furthermore, IL-4 administration and Zn supplementation in rats with Zn deficiency elicited comparable beneficial effects on GALT function, suggesting that the administration of either IL-4 or Zn could prevent inflammatory response via bacterial translocation to the liver.

Effect of high-fat diet on IgA+ cells and BAFF/APRIL in small intestinal villous lamina propria of mice

Obesity exacerbates susceptibility to infectious diseases. We investigated the effects of a high-fat diet (HFD) on intestinal immunity, particularly immunoglobulin (Ig)A-producing cells, B-cell activating factor (BAFF), and a proliferation-inducing ligand (APRIL) localization. Mice (4- to 20-weeks old) were fed HFD or standard chow diet, and their jejunum and ileum were fixed using the in vivo cryotechnique. Immunohistochemistry was performed for IgA, BAFF, and APRIL. In the HFD group, IgA+, IgA+CD22+ (p < 0.001), and IgA+CD138- (p = 0.007) cell counts were diminished in the middle sections of the lamina propria of jejunal villi, and BAFF levels were significantly reduced in jejunal villi. The HFD effects on IgA+ cell distribution seem to be confined to jejunal villi, hinting at localized vulnerabilities in intestinal immunity during obesity. Moreover, in the HFD group, IgA+ B-cell counts were reduced in the middle jejunum, indicating inhibition of the IgA+ B-cells through a T-cell-independent pathway.

Immunomodulatory Effects of a Standardized Botanical Mixture Comprising Angelica gigas Roots and Pueraria lobata Flowers Through the TLR2/6 Pathway in RAW 264.7 Macrophages and Cyclophosphamide-Induced Immunosuppression Mice

Background: As the population ages, enhancing immune function is crucial to mitigating age-related physiological decline. Since immunostimulant drugs are known to have potential side effects, medicinal plants emerge as promising candidates offering a safer alternative. To leverage the advantages of medicinal plants with fewer side effects and develop a potent immune-enhancing agent, we investigated the efficacy of a novel immunomodulatory candidate derived from the combination of Angelica gigas and Pueraria lobata (CHL). Methods: In vitro, CHL was treated in RAW 264.7 macrophages at various time points, and the experiments conducted in the study were performed using ELISA, Western blot, and RT-qPCR analysis. In vivo, C57BL/6 mice were administrated CHL for 16 days (p.o.) and CTX on the three days (i.p.), and experiments were conducted with ELISA, western blot, RT-qPCR analysis, H&E staining, flow cytometry, gut microbiome, and correlation analysis. Results: In vitro, CHL has upregulated NO and cytokines expression, substantially enhancing the NF-κB and MAPK activation. Furthermore, CHL promoted the TAK1, TRAF6, and MyD88 via TLR2/6 signaling. In vivo, the CHL improved the reduced body weight and immune organs' indices and recovered various cytokines expression, NK cell cytotoxicity activity, and immune cell population. CHL also improved the histological structure and tight junction markers, mucin-2, and TLR2/6 in the intestines of CTX-induced mice. Conclusions: Overall, CHL demonstrated immunostimulatory potential by enhancing immune responses and restoring immune function, suggesting its promise as a safe and effective immune-enhancing agent.

PGLYRP1-mediated intracellular peptidoglycan detection promotes intestinal mucosal protection

Peptidoglycan recognition proteins (PGLYRPs) are implicated in the control of the intestinal microbiota; however, molecular requirements for peptidoglycan (PGN) binding and receptor signaling mechanisms remain poorly understood. Here we show that PGLYRP1 is a receptor for the disaccharide motif of lysine N-acetylglucosamine N-acetylmuramic tripeptide (GMTriP-K). PGLYRP1 is required for innate immune activation by GMTriP-K but not muramyl dipeptide (MDP). In macrophages, intracellular PGLYRP1 complexes with NOD2 and GEF-H1, both of which are required for GMTriP-K-regulated gene expression. PGLYRP1 localizes to the endoplasmic reticulum and interacts at the Golgi with NOD2 upon GMTriP-K stimulation. PGLYRP1 and dependent gene expression signatures are induced in both mouse intestinal inflammation and human ulcerative colitis. Importantly, PGLYRP1 activation by GMTriP-K can result in the protection of mice from TNBS-induced colitis. Mammalian PGLYRPs can function as intracellular pattern recognition receptors for the control of host defense responses in the intestine.

Biomarker expression level changes within rectal gut-associated lymphoid tissues in spinal cord-injured rats

Neurogenic bowel dysfunction (NBD) is common after spinal cord injury (SCI). Gut-associated lymphoid tissue (GALT), an organized structure within the mucosal immune system, is important for the maintenance of gut homeostasis and body health and serves as the first line barrier/defense against diet antigens, commensal microbiota, pathogens, and toxins in mucosal areas. The current study examined gene expression levels along six segments of anorectal tissue using real-time polymerase chain reaction (RT-PCR) in uninjured rats (28-day sham surgical controls) and at both 28- and 42-days post-T9 contusion injury. Consistent with our previous report of functional regional differences in the ano-rectum, we demonstrate the existence of GALTs located primarily within the segment at 3-4.5 cm from the rectal dentate line (termed rectal GALTs-rGALTs) in shams with upregulated gene expression levels of multiple biomarkers, including B cell and T cell-related genes, major histocompatibility complex (MHC) class II molecules, and germinal center (GC)-related genes, which was further confirmed by histologic examination. In the same rectal tissue segment following T9 SCI, inflammation-related genes were upregulated at 28 days post-injury (DPI) indicating that microbial infection and inflammation of rGALTs modified structure and function of rGALTs, while at 42 DPI rGALTs exhibited resolution of inflammation and impaired structure/function for extrafollicular B cell responses. Taken together, our data suggest that rGALTs exists in rat rectum for homeostasis of gut microbiota/barrier. SCI induces microbial infection and inflammation in rectal tissues containing rGALTs, which could contribute to development of SCI-related gut microbiome dysbiosis, NBD, and systemic diseases.

Bi-directional communication between intrinsic enteric neurons and ILC2s inhibits host defense against helminth infection

Emerging studies reveal that neurotransmitters and neuropeptides play critical roles in regulating anti-helminth immune responses, hinting at the potential of intrinsic enteric neurons (iENs) in orchestrating intestinal immunity. Whether and how iENs are activated during infection and the potential neuroimmune interactions involved remain poorly defined. Here, we found that helminth infection activated a subset of iENs. Single-nucleus RNA sequencing (snRNA-seq) of iENs revealed alterations in the transcriptional profile of interleukin (IL)-13R+ intrinsic primary afferent neurons (IPANs), including the upregulation of the neuropeptide β-calcitonin gene-related peptide (CGRP). Using genetic mouse models and engineered viral tools, we demonstrated that group 2 innate lymphoid cell (ILC2)-derived IL-13 was required to activate iENs via the IL-13R, leading to iEN production of β-CGRP, which subsequently inhibited ILC2 responses and anti-helminth immunity. Together, these results reveal a previously unrecognized bi-directional neuroimmune crosstalk in the intestine between a subset of iENs and ILC2s, which influences pathogen clearance.

IgA facilitates the persistence of the mucosal pathogen Helicobacter pylori

IgA antibodies have an important role in clearing mucosal pathogens. In this study, we have examined the contribution of IgA to the immune control of the gastrointestinal bacterial pathogens Helicobacter pylori and Citrobacter rodentium. Both bacteria trigger a strong local IgA response that results in bacterial IgA coating in mice and in gastritis patients. Class switching to IgA depends on Peyer's patches, T-cells, eosinophils, and eosinophil-derived TGF-β in both models. In the case of H. pylori, IgA secretion and bacterial coating also depend on a functional bacterial type IV secretion system, which drives the generation of Th17 cells and the IL-17-dependent expression of the polymeric immunoglobulin receptor PIGR. IgA-/- mice are hypercolonized with C. rodentium in all examined tissues, suffer from more severe weight loss and develop more colitis. In contrast, H. pylori is controlled more efficiently in IgA-/- mice than their WT counterparts. The effects of IgA deficiency of the offspring can be compensated by maternal IgA delivered by WT foster mothers. We attribute the improved immune control observed in IgA-/- mice to IgA-mediated protection from complement killing, as H. pylori colonization is restored to wild type levels in a composite strain lacking both IgA and the central complement component C3. IgA antibodies can thus have protective or detrimental activities depending on the infectious agent.

Cross-tissue multi-omics analyses reveal the gut microbiota's absence impacts organ morphology, immune homeostasis, bile acid and lipid metabolism

The gut microbiota influences host immunity and metabolism, and changes in its composition and function have been implicated in several non-communicable diseases. Here, comparing germ-free (GF) and specific pathogen-free (SPF) mice using spatial transcriptomics, single-cell RNA sequencing, and targeted bile acid metabolomics across multiple organs, we systematically assessed how the gut microbiota's absence affected organ morphology, immune homeostasis, bile acid, and lipid metabolism. Through integrated analysis, we detect marked aberration in B, myeloid, and T/natural killer cells, altered mucosal zonation and nutrient uptake, and significant shifts in bile acid profiles in feces, liver, and circulation, with the alternate synthesis pathway predominant in GF mice and pronounced changes in bile acid enterohepatic circulation. Particularly, autophagy-driven lipid droplet breakdown in ileum epithelium and the liver's zinc finger and BTB domain-containing protein (ZBTB20)-Lipoprotein lipase (LPL) (ZBTB20-LPL) axis are key to plasma lipid homeostasis in GF mice. Our results unveil the complexity of microbiota-host interactions in the crosstalk between commensal gut bacteria and the host.

Transport functions of intestinal lymphatic vessels

Lymphatic vessels are crucial for fluid absorption and the transport of peripheral immune cells to lymph nodes. However, in the small intestine, the lymphatic fluid is rich in diet-derived lipids incorporated into chylomicrons and gut-specific immune cells. Thus, intestinal lymphatic vessels have evolved to handle these unique cargoes and are critical for systemic dietary lipid delivery and metabolism. This Review covers mechanisms of lipid absorption from epithelial cells to the lymphatics as well as unique features of the gut microenvironment that affect these functions. Moreover, we discuss details of the intestinal lymphatics in gut immune cell trafficking and insights into the role of inter-organ communication. Lastly, we highlight the particularities of fat absorption that can be harnessed for efficient lipid-soluble drug distribution for novel therapies, including the ability of chylomicron-associated drugs to bypass first-pass liver metabolism for systemic delivery. In all, this Review will help to promote an understanding of intestinal lymphatic-systemic interactions to guide future research directions.

Segmental Regulation of Intestinal Motility by Colitis and the Adaptive Immune System in the Mouse Ileum and Colon

Gastrointestinal motility disturbances are a hallmark of inflammatory bowel disease (IBD); however, their mechanisms remain unclear. This study used a dextran sulfate sodium-induced colitis mouse model, deficient in mature B and T lymphocytes, to assess intestinal motility and the role of the adaptive immune system in health and IBD. In healthy mice, the absence of adaptive lymphocytes reduced acetylcholine (ACh) sensitivity in the ileum. During colitis, it decreases motility by reducing the intensity and frequency of spontaneous contractions while increasing cholinergic responsiveness. In the proximal colon, adaptive immunity deficiency led to increased contractility and reduced ACh sensitivity in homeostasis, whereas colitis reduced contractile capacity. In the mid colon, immune-deficient mice had reduced ACh sensitivity in homeostasis and exacerbated contractile responses during colitis. In the distal colon, adaptive immunity loss reduced contractility in health and cholinergic responsiveness during colitis. These motility alterations were associated with altered acetylcholinesterase and M2/M3 muscarinic receptor expression. Notably, adaptive lymphocyte deficiency resulted in reduced tissue damage and lower tumor necrosis factor-α expression in the colon during colitis, paralleling intestinal motility changes. Overall, the adaptive immune system critically regulates motility and inflammation across different intestinal segments in IBD.

Organismal mucosal immunology: A perspective through the eyes of game theory

In complex organisms, functional units must interact cohesively to maintain homeostasis, especially within mucosal barriers that house diverse, specialized cell exposed to constant environmental challenges. Understanding how homeostasis at mucosal barriers is maintained and how its disruption can lead to autoimmune diseases or cancer, requires a holistic view. Although omics approaches and systems immunology have become powerful tools, they are not without limitations; interpretations may reflect researchers' assumptions, even if other explanations exist. In this perspective, I propose that applying game theory concepts to mucosal immunology could help interpret complex data, offering fresh perspectives and supporting the exploration of alternative scenarios. By framing the mucosal immune system as a network of strategic interactions with multiple possible outcomes, game theory, which analyzes strategic interactions and decision-making processes, could illuminate novel cell types and functions, cell interactions, and responses to pathogens and commensals, leading to a more comprehensive understanding of immune homeostasis and diseases. In addition, game theory might encourage researchers to consider a broader range of possibilities, reduce the risk of myopic thinking, and ultimately enable a more refined and comprehensive understanding of the complexity of the immune system at mucosal barriers. This perspective aims to introduce game theory as a complementary framework for mucosal immunologists, encouraging them to incorporate these concepts into data interpretation and system modeling.

Serotonin attenuates tumor necrosis factor-induced intestinal inflammation by interacting with human mucosal tissue

The intestine hosts the largest immune system and peripheral nervous system in the human body. The gut‒brain axis orchestrates communication between the central and enteric nervous systems, playing a pivotal role in regulating overall body function and intestinal homeostasis. Here, using a human three-dimensional in vitro culture model, we investigated the effects of serotonin, a neuromodulator produced in the gut, on immune cell and intestinal tissue interactions. Serotonin attenuated the tumor necrosis factor-induced proinflammatory response, mostly by affecting the expression of chemokines. Serotonin affected the phenotype and distribution of tissue-migrating monocytes, without direct contact with the cells, by remodeling the intestinal tissue. Collectively, our results show that serotonin plays a crucial role in communication among gut-brain axis components and regulates monocyte migration and plasticity, thereby contributing to gut homeostasis and the progression of inflammation. In vivo studies focused on the role of neuromodulators in gut inflammation have shown controversial results, highlighting the importance of human experimental models. Moreover, our results emphasize the importance of human health research in human cell-based models and suggest that the serotonin signaling pathway is a new therapeutic target for inflammatory bowel disease.

Impact of Gut Microbiota on Lymphoma: New Frontiers in Cancer Research

The gut microbiome (GMB), which is made up of various microorganisms, plays a crucial role in maintaining the health of the host. Disruptions in this delicate ecosystem, known as microbial dysbiosis, have been linked to various diseases, including hematologic malignancies such as lymphoma. This review article explores the complex relationship between the GMB and the development of lymphoma and highlights its implications for diagnostic and therapeutic approaches. It discusses how GMB influences lymphoma development directly through the presence of certain microorganisms and indirectly through changes in the immune system. The clinical relevance of GMB is highlighted and its potential utility for diagnosis, predicting treatment outcomes and developing personalized therapeutic strategies for lymphoma patients is demonstrated. The review also looks at microbiome-targeted interventions such as fecal microbiome transplantation and dietary modification, which have shown promise for treating microbial dysbiosis and improving patient outcomes. In addition, it highlights the analytical challenges and the need for further research to fully elucidate the mechanistic functions of the GMB in the context of lymphoma. This review emphasizes the critical role of GMB in lymphomagenesis and its potential for the development of diagnostic and therapeutic strategies.

Mouse gut blueprint: regionality and resilience

Mayassi and colleagues utilized spatial transcriptomics to create a comprehensive blueprint of the mouse gut, exploring its adaptability and resilience under perturbed conditions. Their work highlights the adaptive capabilities of the murine gut's regionalized structure, providing insights into how it functions in a coordinated manner and how it responds to external challenges.

Application of Raman Spectroscopy in Non-Invasive Analysis of the Gut Microbiota and Its Impact on Gastrointestinal Health

The gut microbiota, a complex community of microorganisms, plays a crucial role in gastrointestinal (GI) health, influencing digestion, metabolism, immune function, and the gut-brain axis. Dysbiosis, or an imbalance in microbiota composition, is associated with GI disorders, including irritable bowel syndrome (IBS), inflammatory bowel disease (IBD), and colorectal cancer (CRC). Conventional microbiota analysis methods, such as next-generation sequencing (NGS) and nuclear magnetic resonance (NMR), provide valuable insights but are often expensive, time-consuming, and destructive. Raman spectroscopy (RS) is a non-invasive, cost-effective, and highly sensitive alternative. This analytical technique relies on inelastic light scattering to generate molecular "fingerprints", enabling real-time, marker-free analysis of microbiota composition and metabolic activity. This review explores the principles, sample preparation techniques, and advancements in RS, including surface-enhanced Raman spectroscopy (SERS), for microbiota research. RS facilitates identifying microbial species, analysing key metabolites like short-chain fatty acids (SCFA), and monitoring microbiota responses to dietary and therapeutic interventions. The comparative analysis highlights RS's advantages over conventional techniques, such as the minimal sample preparation, real-time capabilities, and non-destructive nature. The integration of RS with machine learning enhances its diagnostic potential, enabling biomarker discovery and personalised treatment strategies for GI disorders. Challenges, including weak Raman signals and spectral complexity, are discussed alongside emerging solutions. As RS technology advances, mainly through portable spectrometers and AI integration, its clinical application in microbiota diagnostics and personalised medicine is poised to transform GI healthcare, bridging microbiota research with practical therapeutic strategies.

Tetrahedral Framework Nucleic Acid Relieves Sepsis-Induced Intestinal Injury by Regulating M2 Macrophages

This study aimed to clarify the role and mechanism of tetrahedral framework nucleic acids (tFNAs) in regulating M2 macrophages to reduce intestinal injury. An intestinal injury model was established by intraperitoneal injection of lipopolysaccharides (LPS) in mice to explore the alleviating effects of tFNAs on intestinal injury. Inflammatory factors were detected by quantitative polymerase chain reaction (qPCR) and enzyme-linked immunosorbent assay (ELISA). The intestinal barrier and permeability were assessed using western blotting and immunohistochemistry. Macrophages in the gut were localised and quantified using immunofluorescence. Western blotting was used to investigate the role and mechanism of tFNAs in regulating macrophages and alleviating inflammation in the injured intestines. These results show that tFNAs attenuated sepsis-induced intestinal injury. tFNAs can also promote the intestinal barrier reconstruction and reduce intestinal permeability. In vivo, tFNAs accelerated the aggregation of M2 macrophages at an early stage of injury and reduced the number of M1 macrophages in the intestine. In addition, tFNAs enhanced the clearance ability of intestinal macrophages. They activated the signalling and transcription activating factor 1(STAT1) and cytokine signalling inhibitory factor 1/3 (SOCS1/3) pathways by increasing the expression of the phagocytic receptor Mertk. These findings indicated that tFNAs can alleviate sepsis-induced intestinal injury by regulating M2 macrophages, providing a new option for treating intestinal injury.

Investigation of Clostridium butyricum on atopic dermatitis based on gut microbiota and TLR4/MyD88/ NF-κB signaling pathway

BACKGROUND

Probiotics, as common regulators of the gut microbiota, have been used in research to alleviate clinical symptoms of atopic dermatitis (AD).

OBJECTIVE

Our research team has previously identified a potential relieving effect of Clostridium butyricum on the treatment of AD, but the specific mechanism of how Clostridium butyricum alleviates AD has not yet been confirmed.

METHODS

In this study, we explored the relieving effect of Clostridium butyricum on AD through in vivo and in vitro experiments. AD mice induced by 2,4-dinitrofluorobenzene (DNFB) were orally administered with 1 × 108 CFU of Clostridium butyricum for three consecutive weeks.

RESULTS

Oral administration of Clostridium butyricum reduced ear swelling, alleviated back skin lesions, decreased mast cell and inflammatory cell infiltration, and regulated the levels of inflammation-related cytokines. Clostridium butyricum activated the intestinal immune system through the TLR4/MyD88/NF-κB signaling pathway, suppressed the expression of inflammatory factors IL-10 and IL-13, and protected the damaged intestinal mucosa.

CONCLUSION

Clostridium butyricum administration improved the diversity and abundance of the gut microbiota, enhanced the functionality of the immune system, and protected the epidermal barrier.

Key Taxa of the Gut Microbiome Associated with the Relationship Between Environmental Sensitivity and Inflammation-Related Biomarkers

Individual differences in environmental sensitivity are linked to stress-related psychiatric symptoms. In previous research, we found that high environmental sensitivity can be a risk factor for increased inflammation and gut permeability, particularly when gut microbiome diversity is low. However, the specific gut bacterial taxa involved in this interaction remain unclear. As a preliminary study, this research aimed to identify the key gut microbiome taxa associated with this relationship. Environmental sensitivity, gut microbiome composition, gut permeability (lipopolysaccharide-binding protein, LBP), and inflammation (C-reactive protein, CRP) biomarkers were evaluated in 88 participants. The interaction between environmental sensitivity and the relative abundance of the family Marinifilaceae (genus Butyricimonas) was a predictor of CRP levels. Similarly, the interaction between environmental sensitivity and relative abundance of the family Barnesiellaceae (genus Coprobacter), the family Akkermansiaceae (genus Akkermansia), the genus Family XIII AD3011 group, the genus GCA-900066225, or the genus Ruminiclostridium 1 predicted LBP levels. Individuals with high environmental sensitivity exhibited elevated CRP or LBP levels when the relative abundance of these taxa was low. Conversely, highly sensitive individuals had lower CRP or LBP levels when the relative abundance of these taxa was high. This study suggests that specific taxa serve as one of the protective factors against inflammation and gut permeability in individuals with high environmental sensitivity. Further in-depth studies are needed to confirm these associations and understand the underlying mechanisms.

Intestinal interstitial fluid isolation provides novel insight into the human host-microbiome interface

AIMS

The gastrointestinal (GI) tract is composed of distinct sub-regions, which exhibit segment-specific differences in microbial colonization and (patho)physiological characteristics. Gut microbes can be collectively considered as an active endocrine organ. Microbes produce metabolites, which can be taken up by the host and can actively communicate with the immune cells in the gut lamina propria with consequences for cardiovascular health. Variation in bacterial load and composition along the GI tract may influence the mucosal microenvironment and thus be reflected its interstitial fluid (IF). Characterization of the segment-specific microenvironment is challenging and largely unexplored because of lack of available tools.

METHODS AND RESULTS

Here, we developed methods, namely tissue centrifugation and elution, to collect IF from the mucosa of different intestinal segments. These methods were first validated in rats and mice, and the tissue elution method was subsequently translated for use in humans. These new methods allowed us to quantify microbiota-derived metabolites, mucosa-derived cytokines, and proteins at their site-of-action. Quantification of short-chain fatty acids showed enrichment in the colonic IF. Metabolite and cytokine analyses revealed differential abundances within segments, often significantly increased compared to plasma, and proteomics revealed that proteins annotated to the extracellular phase were site-specifically identifiable in IF. Lipopolysaccharide injections in rats showed significantly higher ileal IL-1β levels in IF compared to the systemic circulation, suggesting the potential of local as well as systemic effect.

CONCLUSION

Collection of IF from defined segments and the direct measurement of mediators at the site-of-action in rodents and humans bypasses the limitations of indirect analysis of faecal samples or serum, providing direct insight into this understudied compartment.

Early changes in intestinal lymphoid and myeloid populations in experimental autoimmune encephalomyelitis

Intestinal immunity is associated with several autoimmune diseases, such as systemic lupus erythematosus, rheumatoid arthritis, and type 1 diabetes. Recent evidence also suggests its implication in the pathogenesis of autoimmune diseases affecting the central nervous system, such as multiple sclerosis (MS). However, there is ongoing debate regarding which part of the intestinal tract contributes to the development of MS. Therefore, our study aimed to explore the early changes in lymphoid and myeloid immune cells populations in experimental autoimmune encephalomyelitis (EAE), an animal model of MS. We also sought to determine the roles of the colon and/or small intestine in the pathogenesis of EAE. By using flow cytometry, we revealed a transient increase in T and B lymphocytes in the ileal lamina propria of EAE mice just before the onset of motor symptoms. Additionally, we highlighted an increase in dendritic cells and monocytes/macrophages in the colonic lamina propria of EAE animals during the presymptomatic phase. Altogether, our findings indicate that both small intestine and colon are involved in the pathogenesis of EAE, despite engaging distinct immunological processes. This study provides new insights for understanding the roles of intestinal lymphoid and myeloid immune cells on the pathogenesis of MS and other autoimmune diseases.

A spatiotemporal and machine-learning platform facilitates the manufacturing of hPSC-derived esophageal mucosa

Human pluripotent stem cell-derived tissue engineering offers great promise for designer cell-based personalized therapeutics, but harnessing such potential requires a deeper understanding of tissue-level interactions. We previously developed a cell replacement manufacturing method for ectoderm-derived skin epithelium. However, it remains challenging to manufacture the endoderm-derived esophageal epithelium despite possessing a similar stratified epithelial structure. Here, we employ single-cell and spatial technologies to generate a spatiotemporal multi-omics cell census for human esophageal development. We identify the cellular diversity, dynamics, and signal communications for the developing esophageal epithelium and stroma. Using Manatee, a machine-learning algorithm, we prioritize the combinations of candidate human developmental signals for in vitro derivation of esophageal basal cells. Functional validation of Manatee predictions leads to a clinically compatible system for manufacturing human esophageal mucosa.

Immune crosstalk between respiratory and intestinal mucosal tissues in respiratory infections

Mucosal tissues, including those in the respiratory and gastrointestinal tracts, are critical barrier surfaces for pathogen invasion. Infections at these sites not only trigger local immune response, but also recruit immune cells from other tissues. Emerging evidence in the mouse models and human samples indicates that the immune crosstalk between the lung and gut critically impacts and determines the course of respiratory disease. Here we summarize the current knowledge of the immune crosstalk between the respiratory and gastrointestinal tracts, and discuss how immune cells are recruited and migrate between these tissues during respiratory infections. We also discuss how commensal bacteria contribute to these processes.

Leveraging thiol-functionalized biomucoadhesive hybrid nanoliposome for local therapy of ulcerative colitis

Directly administering medication to inflamed intestinal sites for treating ulcerative colitis (UC), poses significant challenges like retention time, absorption variability, side effects, drug stability, and non-specific delivery. Recent advancements in therapy to treat colitis aim to improve local drug availability that is enema therapy at the site of inflammation, thereby reducing systemic adverse effects. Nevertheless, a key limitation lies in enemas' inability to sustain medication in the colon due to rapid peristaltic movement, diarrhea, and poor local adherence. Therefore, in this work, we have developed site-specific thiolated mucoadhesive anionic nanoliposomes to overcome the limitations of conventional enema therapy. The thiolated delivery system allows prolonged residence of the delivery system at the inflamed site in the colon, confirmed by the adhesion potential of thiolated nanoliposomes using in-vitro and in-vivo models. To further provide therapeutic efficacy thiolated nanoliposomes were loaded with gallic acid (GA), a natural compound known for its antibacterial, antioxidant, and potent anti-inflammatory properties. Consequently, Gallic Acid-loaded Thiolated 2,6 DALP DMPG (GATh@APDL) demonstrates the potential for targeted adhesion to the inflamed colon, facilitated by their small size 100 nm and anionic nature. Therapeutic studies indicate that this formulation offers protective effects by mitigating colonic inflammation, downregulating the expression of NF-κB, HIF-1α, and MMP-9, and demonstrating superior efficacy compared to the free GA enema. The encapsulated GA inhibits the NF-κB expression, leading to enhanced expression of MUC2 protein, thereby promoting mucosal healing in the colon. Furthermore, GATh@APDL effectively reduces neutrophil infiltration and regulates immune cell quantification in colonic lamina propria. Our findings suggest that GATh@APDL holds promise for alleviating UC and addressing the limitations of conventional enema therapy.

The renaissance of oral tolerance: merging tradition and new insights

Oral tolerance is the process by which feeding of soluble proteins induces antigen-specific systemic immune unresponsiveness. Oral tolerance is thought to have a central role in suppressing immune responses to 'harmless' food antigens, and its failure can lead to development of pathologies such as food allergies or coeliac disease. However, on the basis of long-standing experimental observations, the relevance of oral tolerance in human health has achieved new prominence recently following the discovery that oral administration of peanut proteins prevents the development of peanut allergy in at-risk human infants. In this Review, we summarize the new mechanistic insights into three key processes necessary for the induction of tolerance to oral antigens: antigen uptake and transport across the small intestinal epithelial barrier to the underlying immune cells; the processing, transport and presentation of fed antigen by different populations of antigen-presenting cells; and the development of immunosuppressive T cell populations that mediate antigen-specific tolerance. In addition, we consider how related but distinct processes maintain tolerance to bacterial antigens in the large intestine. Finally, we outline the molecular mechanisms and functional consequences of failure of oral tolerance and how these may be modulated to enhance clinical outcomes and prevent disease.